1. Field of the Invention
The present invention relates to a camera, and more particularly, to a camera equipped with a lens protection barrier (i.e., a lens cover) that opens and closes in front of a lens barrel that holds a photographic lens.
2. Description of Related Art
With so-called collapsible-mount-type cameras, a lens barrel of the camera scrolls into a position within the camera body when the camera is not in use and scrolls out to a position protruding from the camera body when the camera is in use. Various known lens barriers can selectively cover the front side of the lens barrel, or can be opened and closed to protect the photographic lens.
One such lens barrier is disclosed in Japanese Patent publication No. 62-113335. This kind of lens barrier opens by moving along the front side of the camera to withdraw from the surface of the photographic lens when the camera is in use, and closes by moving in the opposite direction to cover the surface of the photographic lens when the lens barrel is collapsed and withdrawn into the camera body when the camera is not in use.
In such collapsible-mount-type cameras, however, a problem can arise during opening and closing of the lens barrier. Damage can occur because of interference or collision between the lens barrier and the lens barrel when an attempt is made to close the lens barrier while the lens barrel holding the photographic lens is scrolled out and protrudes from the camera, or when an attempt is made to scroll out the lens barrel while the barrier is closed.
To prevent this problem, a known camera, disclosed in Japanese Patent publication No. 1-288842, includes a lens barrier on the front of the camera that can be slid manually along the front of the camera so as to withdraw from the front of the photographic lens when the camera is in use. When the camera is not in use, the barrier can be slid along the front of the camera so as to cover the front of the photographic lens when the lens barrel is collapsed and withdrawn into the body of the camera.
The barrier of this conventional camera cannot be closed when the lens barrel is scrolled out and protrudes from the camera. A detection device continuously detects whether the barrier is in an open position or a closed position, so that scrolling the lens barrel out is allowed only when the barrier is open, that is, only when the barrier has been withdrawn from in front of the photographic lens. However, in this conventional camera, although manual closing of the barrier is only permitted when the lens barrel has been scrolled in and is in the collapsed state, manual opening and closing of the barrier is still required. Although the structure is simple, problems related to manual operation can still arise during operation of the camera.
To address these problems, recent cameras include a drive source, such as an electric motor, to automate the operations of scrolling the lens barrel in and out and opening and closing the lens barrier. Additional problems can arise in such automated cameras because damage can occur due to interference and collision between the lens barrier and the lens barrel.
In one known camera, the front of the lens barrel is selectively covered by the lens barrier, and a cam is provided for closing the barrier. The cam is also part of the drive mechanism used to drive the lens barrel during scrolling of the lens barrel in and out of the camera body. Opening and closing of the barrier and movement of the lens barrel are thus linked. Problems can arise with this kind of conventional structure, however, because the closing of the barrier is linked to the scrolling action of the lens barrel. When the lens barrel is driven by means of a helicoid (i.e., a screw drive), for example, after the lens barrel has been withdrawn to a position where the barrier can move in front of it, to close the barrier it is necessary to additionally rotate the helicoid through a preset amount of rotation. This causes the lens barrel to move farther in the collapsing direction than necessary, by the amount of the additional rotation required to close the barrier. As a result, the additional space where the lens barrel moves is wasted. Other components of the camera cannot be positioned in that space, presenting design-related problems and making the camera less compact.
On the other hand, when the lens barrel is driven by a cam ring, it is possible to eliminate the wasted space by taking into consideration the shape of cam grooves on the cam ring so that the lens barrel does not move forward or backward even when the cam ring rotates. To keep the lens barrel from moving forward or backward, however, it is necessary for the rear edge of the cam groove to face the perimeter of the cam ring. Because there are limits to the groove width and number of cam grooves that can be formed on the cam ring, limitations are placed on the freedom of design in this type of lens barrel as well.
It is particularly desirable to overcome problems such as those described above when the scrolling of the lens barrel in and out and the opening and closing of the lens barrier are automated by a drive source, such as an electric motor.
Furthermore, with the lens barriers described above, when the lens barrier is in the closed position covering the front of the lens barrel, there are times when an unanticipated external force is applied. It is desirable to prevent the effects of this external force. It is possible to protect the lens barrier and camera body from external forces by preventing the lens barrier from moving towards its open position, or by smoothly moving the lens barrier to its open position without opposing the external force.
An example of a model in which movement towards the open position is prevented, even in the presence of an external force on the lens barrier, is disclosed in Japanese Patent publication No. 4-301544. When the lens barrier covers the front of the lens barrel, the opening in the camera body cover is completely plugged and the barrier does not open, even if an external force is applied. This structure is advantageous because the camera body is sealed, stable and has a fully flat design, enabling it to fit easily into its carrying case.
Because a convex part that covers and uncovers the camera body opening is provided on the lens barrier, however, plugging the cover opening as described above requires moving the lens barrier in the direction of the optic axis. Moreover, it also is necessary to link the lens barrier motion with the scrolling in and out of the lens barrel, making the structure complex and increasing cost. Furthermore, space is needed to accommodate movement of the barrier in the direction of the optic axis, making the camera less compact.